Patent GB-108988-A (GB)
Title: Improvements in or relating to Light Projection Apparatus.
Inventor: AMES ADELBERT
IPC: F21V11/16
Filed: 1916-12-06
Abstract: 108,988. Ames, A. Dec. 6, 1916. Vehicular lanterns.-In an automobile or like head-light., the source of light is positioned with respect to the focus of the reflector so as to obtain a concentrated horizontal beam with a slight divergence, and the rays of light, which would otherwise be projected upwardly, are projected downwardly by refracting-means interposed in their path before they strike the parabolic reflector. Fig. 1 shows one form in which a V-shaped light source is positioned with its apex in the focus of the reflector P, and with its rearwardlyextending legs respectively above and below the axis of the reflector. The refractor 2 is arranged between the light source and the upper half of the reflector, and extends downwardly somewhat below the lowest point of the light source. The refractor consists of a front spherical part 6, Fig. 3, of uniform thickness having its centre of curvature behind the light source, a rear substantially spherical part 11 of substantially uniform thickness having the centres of curvature of its outer and inner surfaces in front of the light source, and an intermediate thickened part having its outer surface 8 tangential to the part 6 and its rear face 10 in a plane intersecting the axis of the reflector in front of the light source. The outer surface of the part 11 may be silvered, or a refleeting-part 24, Fig. 1, may be formed on the support 17 for the refractor. The lower lateral edge 16, Fig. 3, of the refractor may be bevelled and coated with silver. The front of the refractor is preferably coated to prevent light from being radiated upwardly and forwardly, and the light radiated laterally and approximately horizontally is diffused by frosting the inner surface of the corresponding part 4, Fig. 1, of the refractor or .by coating it, for example with black balsam. The support 17 has preferably a peripheral flange 22<a>, Fig. 5, for engaging a shoulder 12, Fig. 3, on the refractor, and is secured on the lamp socket or the lamp-holder by means of a bolt passing through struck-up lugs 22 on the lower parts 18 of the support 17, which parts 18 may be light-reflecting or light-absorbing. When the lower leg of the V-shaped light source is arranged in the axis of the reflector instead of below it, the frosting of the part 4 and the bevelling of the part 16 are preferably dispensed with. The electric filament is disposed in the lamp bulb in such a position that any light rays reflected from the surface of the bulb crosses the horizontal plane through the axis of the reflector on the same side of its focus as the light source. In a second form in which the V-shaped light source is arranged axially in front of the focus of a paraboloidal reflector, the refractor is positioned below the light source and is formed with a front part 36, Fig. 10, of substantially uniform section and with annular prisms 29, 34, 35, the rear surfaces of which are curved or have each three parts 31, 32, 33 of different slopes. The front surfaces 56, 57 of the prisms 34, 35 are preferably in planes which intersect one another below and behind the light source, and the front surfaces 54, 53 of the prism 29 and a rear flange are preferably in planes which intersect one another above and behind the light source. The upper inner edges 39 of the refractor are bevelled, and the refractor is supported similarly to that shown in Fig. 1. In a modification, the front part of the refractor is dispensed with. In a third form in which the light source is arranged horizontally, an annular prism 42, Fig. 14, of triangular cross-section is arranged between the light source and the upper part of the reflector P, the rays being refracted and reflected as indicated. When employing cylindrical lamp bulbs, an annular prism, having an inner cylindrical surface, is arranged above or below the lamp bulb.